package lily.phs.vaccination;


import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

public class VaccinationScrollLayout extends ViewGroup{
	private static final String TAG="ScrollLayout";
	private Scroller mScroller;
	private int mTouchSlop;
	private VelocityTracker mVelocityTracker;
	private int mCurScreen;
	private int mDefaultScreen=0;
	private float mLastMotionX;
	private float mLastMotionY;
	private static final int TOUCH_STATE_REST = 0;  
    private static final int TOUCH_STATE_SCROLLING = 1;      
    private static final int SNAP_VELOCITY = 600;  
    private int mTouchState = TOUCH_STATE_REST;  
   
	
	public VaccinationScrollLayout(Context context,AttributeSet attrs) {
		this(context,attrs,0);
		// TODO Auto-generated constructor stub
	}
	public VaccinationScrollLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context,attrs,defStyle);
		// TODO Auto-generated constructor stub
		mScroller=new Scroller(context);
		mCurScreen=mDefaultScreen;
		mTouchSlop=ViewConfiguration.get(getContext()).getScaledTouchSlop();
		
	}
	@Override
	protected void onLayout(boolean changed, int arg1, int arg2, int arg3, int arg4) {
		// TODO Auto-generated method stub
		int childLeft=0;
		final int childCount=getChildCount();
		for(int i=0;i<childCount;i++){
			final View childView=getChildAt(i);
			if(childView.getVisibility()!=View.GONE);{
				final int childWidth=childView.getMeasuredWidth();
				childView.layout(childLeft, 0, childLeft+childWidth, childView.getMeasuredHeight());
				childLeft+=childWidth;
			}
		}	
	}
	protected void onMeasure(int widthMeasureSpec,int heightMeasureSpec){
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		final int width=MeasureSpec.getSize(widthMeasureSpec);
		final int widthMode=MeasureSpec.getMode(widthMeasureSpec);
		if(widthMode!=MeasureSpec.EXACTLY){
			throw new IllegalStateException("ScrollLayout only can run at EXACTLY mode!");
		}
		final int heightMode=MeasureSpec.getMode(heightMeasureSpec);
		if(heightMode!=MeasureSpec.EXACTLY){
			throw new IllegalStateException("ScrollLayout only can run at EXACTLY mode!");
		}
		final int childCount=getChildCount();
		for(int i=0;i<childCount;i++){
			getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
		}
		scrollTo(mCurScreen*width,0);
	}
	/** 
     * According to the position of current layout 
     * scroll to the destination page. 
     */ 
	public void snapToDestination(){
		final int screenWidth=getWidth();
		final int destScreen=(getScrollX()+screenWidth/2)/screenWidth;
		snapToScreen(destScreen);
	}
	public void snapToScreen(int whichScreen){
		whichScreen=Math.max(0, Math.min(whichScreen,getChildCount()-1));
		if(getScrollX()!=(whichScreen*getWidth())){
			final int delta=whichScreen*getWidth()-getScrollX();
			mScroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta)*2);
			mCurScreen=whichScreen;
			invalidate();
		}
	}
	public void setToScreen(int whichScreen){
		whichScreen=Math.max(0, Math.min(whichScreen, getChildCount()-1));
		mCurScreen=whichScreen;
		scrollTo(whichScreen*getWidth(),0);
	}
	public int getCurScreen(){
		return mCurScreen;
	}
	public void computeScroll(){
		// TODO Auto-generated method stub  
        if (mScroller.computeScrollOffset()) {  
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());  
            postInvalidate();
        }
	}
	public boolean onTouchEvent(MotionEvent event){
		if(mVelocityTracker==null){
			mVelocityTracker=VelocityTracker.obtain();
		}
		mVelocityTracker.addMovement(event);
		final int action=event.getAction();
		final float x=event.getX();
		final float y=event.getY();
		switch(action){
		case MotionEvent.ACTION_DOWN: Log.e(TAG, "event down");
			if(!mScroller.isFinished()){
				mScroller.abortAnimation();
			}
			mLastMotionX=x;
			break;
		case MotionEvent.ACTION_MOVE:
			int deltaX=(int)(mLastMotionX-x);
			mLastMotionX=x;
			scrollBy(deltaX,0);
			break;
		case MotionEvent.ACTION_UP:
			Log.e(TAG, "event : up"); 
			final VelocityTracker velocityTracker = mVelocityTracker;     
            velocityTracker.computeCurrentVelocity(1000);     
            int velocityX = (int) velocityTracker.getXVelocity();     
            Log.e(TAG, "velocityX:"+velocityX);  
            if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {     
                // Fling enough to move left     
                Log.e(TAG, "snap left");  
                snapToScreen(mCurScreen - 1);     
            } else if (velocityX < -SNAP_VELOCITY     
                    && mCurScreen < getChildCount() - 1) {     
                // Fling enough to move right     
                Log.e(TAG, "snap right");  
                snapToScreen(mCurScreen + 1);     
            } else {     
                snapToDestination();     
            }     
            if (mVelocityTracker != null) {     
                mVelocityTracker.recycle();     
                mVelocityTracker = null;     
            }     
            // }     
            mTouchState = TOUCH_STATE_REST;     
            break;  
        case MotionEvent.ACTION_CANCEL:  
            mTouchState = TOUCH_STATE_REST;  
            break;
		}
		return true;
	}
	public boolean onInterceptTouchEvent(MotionEvent ev) {  
        // TODO Auto-generated method stub  
        Log.e(TAG, "onInterceptTouchEvent-slop:"+mTouchSlop);  
          
        final int action = ev.getAction();  
        if ((action == MotionEvent.ACTION_MOVE) &&   
                (mTouchState != TOUCH_STATE_REST)) {  
            return true;  
        }  
          
        final float x = ev.getX();  
        final float y = ev.getY();  
          
        switch (action) {  
        case MotionEvent.ACTION_MOVE:  
            final int xDiff = (int)Math.abs(mLastMotionX-x);  
            if (xDiff>mTouchSlop) {  
                mTouchState = TOUCH_STATE_SCROLLING;  
                  
            }  
            break;  
              
        case MotionEvent.ACTION_DOWN:  
            mLastMotionX = x;  
            mLastMotionY = y;  
            mTouchState = mScroller.isFinished()? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;  
            break;  
              
        case MotionEvent.ACTION_CANCEL:  
        case MotionEvent.ACTION_UP:  
            mTouchState = TOUCH_STATE_REST;  
            break;  
        }  
          
        return mTouchState != TOUCH_STATE_REST;  
    }

}
